Publikationen

Novel films consist of multi-walled carbon nanotubes (MWCNT) were fabricated by means of catalytic chemical vapor deposition (CVD) technique with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene (FeCp2) as catalyst. The electrochemical and thermodynamic behavior of the ferrocyanide/ferricyanide, [Fe(CN)(6)](3-/4-) redox couple on synthesized MWCNT-based films was investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques at T = (278.15, 283.15, 293.15, and 303.15) K. The redox couple [Fe(CN)(6)](3-/4-) behaves quasi-reversibly on fabricated MWCNT-based films and its reversibility is enhanced upon increasing temperature. Namely, the findings establish that with the rise in temperature the barrier for interfacial electron transfer decreases, leading, consequently, to an enhancement of the kinetics of the charge transfer process. According to thermodynamics the equilibrium of the redox process is shifted towards the formation of [Fe(CN)(6)](3-) at elevated temperatures.

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of the chemical vapor deposition technique with decomposition of either acetonitrile (ACN) or benzene (BZ) in the presence of ferrocene (FeCp2) which served as catalyst. The electrochemical response of the two different kinds of MWCNT-based films, further referred to as MWCNT-ACN and MWCNT-BZ, towards the oxidation of dopamine (DA) to dopamine-o-quinone (DAQ) was tested by means of cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Both MWCNT-based films exhibit quasi-reversible response towards DA/DAQ with some slight kinetic differences; specifically, the charge-transfer process was found to be faster on MWCNT-ACN (k (s) = 35.3 × 10(-3) cm s(-1)) compared to MWCNT-BZ (k (s) = 6.55 × 10(-3) cm s(-1)). The detection limit of MWCNT-BZ for DA (0.30 mu M) appears to be poorer compared to that of MWCNT-ACN (0.03 mu M), but nevertheless, both MWCNT-based films exhibit greater detection ability compared to other electrodes reported in the literature. The sensitivities of MWCNT-ACN and MWCNT-BZ towards DA/DAQ were determined as 0.65 and 0.22 A M-1 cm(-2), respectively. The findings suggest that the fabricated MWCNT-based electrodes can be successfully applied for the detection of molecules with biological interest.

Films of vertically aligned multi-walled carbon nanotubes (MWCNT) were selectively synthesized on silicon dioxide substrate by catalytic chemical vapor deposition using either benzene or acetonitrile as carbon source and ferrocene (1% w/w) as catalyst. The MWCNT were extensively characterized by using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Raman spectroscopy. In order to examine the prospective application of the fabricated MWCNT films for the detection of electro-active compounds in organic solvent media, electrochemical studies of the oxidation of cobaltocene (CoCp(2)) to cobaltocenium cation (CoCp (2) (+)) (Cp = cyclopentadienyl anion) in acetonitrile were performed on these films. For this purpose, cyclic voltammetry and electrochemical impedance spectroscopy were employed. The electrochemical parameters for the CoCp (2) (+/0) couple in acetonitrile were derived and compared with those obtained using a conventional glassy carbon electrode. The results demonstrate that the synthesized MWCNT films are promising electrode materials for the electrochemical detection of electro-active species in organic solvents. The MWCNT film formed upon decay of benzene has higher capacitance, less Warburg impedance, and less charge transfer resistance, and consequently it provides faster electron transfer kinetics.

Solutions of palladium chloride in acetonitrile are investigated by means of electrospray ionization mass spectrometry (ESI-MS). In contrast to several other metal salts previously investigated using ESI-MS, PdCl(2)2 has a pronounced tendency for aggregation to yield [Pd(m)Cl(2m-1)(CH(3)CN)(n)](+) clusters in the positive ion mode and [Pd(m)Cl(2m+1)](-) clusters when the negative ions are sampled, respectively. The observation of these oligomers parallels polymeric structures of PdCl(2) in the solid phase. The positive ions are most abundant for m = 2 and generally associated with several molecules of the solvent, whereas many different cluster sizes occur for the anions which generally do not appear as solvent associates. Parallel conductivity measurements in the condensed phase lend support to a pronounced tendency for aggregation of PdCl(2) in acetonitrile solution.

In the present article, the electrochemical sensitivity and response of films consisting of carbon nanoparticles were examined to test their potential applications as electrode materials for the construction of electrochemical sensors. For this purpose, a film of vertically aligned multi-walled carbon nanotubes (MWCNTs) on silicon dioxide substrate was synthesized by means of catalytic chemical vapor deposition (CVD) at 900oC using ferrocene (FeCp2) as catalyst and acetonitrile (ACN) as a carbon source. Furthermore, bucky-paper (BP) film was produced upon ultrasonic treatment of aqueous solution of single-walled carbon nanotubes (SWCNTs) in the presence of sodium dodecyl sulfate (SDS) micelle. In order to examine the electrochemical activity of the fabricated films, electrochemical studies of the oxidation of ferrocene (FeCp2) to ferrocenium cation (FeCp2+) (where Cp denotes cyclopentadienyl anion) in ACN containing n-tetrabutylammonium hexafluorophosphat (NBu4PF6) as supporting electrolyte were performed. For the electrochemical experiments the techniques of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed. The electrochemical parameters of the FeCp2+/0 redox couple in ACN on the fabricated films were determined and compared with those obtained using conventional glassy carbon (GC) electrode. The results demonstrate that the FeCp2+/0 redox couple exposes Nernstian response on either MWCNT or GC electrodes while its response on BP film can be recognized as near Nernstian. The findings verify that the synthesized MWCNT and BP films hold promising and important applications in electro-analytical chemistry.